What? A wearable display with a basic liquid crystal as well to control opacity can trivially do a normal rectangle too, anywhere you want. It's a complete superset of all current displays, that's the most basic use of it. Doing 3D stuff or whatever if anything strikes me as by far the least important, at least for quite a while after intro most of its use would be simple HUD or just using what we've got except wherever. Right now as I type this I'm sitting at a desk in front of a 5k 27" rectangle. With refined retinal scanning display glasses, I could be sitting on a couch or somewhere else, and still have a 27" 5k equivalent rectangle to pull up (or 36" 8k or whatever I wanted) rather then a 6-7" display (phone) or 14-16" (notebook) at much lower resolution. Decent wireless keyboards and mice exist and could be further improved on.
Can you explain why people think "3D" is an important aspect of these? AR/VR would already pay for itself just by being able to bring up my desktop (or smaller individual windows or anything) anywhere, more efficiently.